I just got done brewing my 4th batch ever. My first 3 went very well. Today not so much. Missed my mash temp by 2ºF was aiming for 154 got 152. First time i've missed my mash temp. I collect my boil volume of 6.75 Gallons. When my boil is finished I'm looking at it like WOW thats not 5 gallons. Sure enough my 60 minute boil got me down to 4 gallons. So i had 2.75 gallons of boil off. WTF? Also my target gravity was 1.057. Even with all that boil off i only got 1.061. I only got 64% efficiency. Most of my beers have been 76-78 range.

So not only did i have crazy boil off i had about a 12% decrease in efficiency. I am confused by that. I figure out I do get about 1.25 to 1.5 gallons of boil off during the normal 60 minute boil or that has been my average. I'm just confused about this crazy amount of boil off and terrible efficiency.

Believe me, it could be much worse. You still have beer. I've seen several people on here talk about a bad brew day experience that ended with a major spill, broken carboy etc.
Chalk this up as a lesson learned, and make a great next batch.

Yeah, that's not too bad. I've had worse and heard of worse and mine still turned out pretty damn good. Missing your mash by 2 won't kill your beer and some people don't even worry about their efficiency and instead just focus on consistency of their techniques. I've definitely missed my OGs by more and once again.......it was a great beer!

Were you brewing outside? I find that cold, windy weather can greatly increase my boil-off.

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Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"

That's brew day with a few hiccups. I got all the way through a perfect mash,boil, into a good chill on my deck on a beautiful fall day, only to realize way too late that a hose clamp on my immersion chiller gave way and filled what should have been a 5gal batch up to 12gal. I. Tryed fermenting it out anyways but had no action at all. First and only dumped batch!!!

That's brew day with a few hiccups. I got all the way through a perfect mash,boil, into a good chill on my deck on a beautiful fall day, only to realize way too late that a hose clamp on my immersion chiller gave way and filled what should have been a 5gal batch up to 12gal. I. Tryed fermenting it out anyways but had no action at all. First and only dumped batch!!!

Out of sheer curiosity...anyone know what would have happened had he reboiled it down?

Granted we are looking at a 3,5 maybe 7+ hour boil (depending on boiloff)...but curious if it would have worked.

I thought about that too jay and just didn't add it to the story the SG was very very low. After I weighed out the cost of propane vs how much I spent on the batch, it was worth it to eat the batch cost and live to brew another day.